Engine improvements



June 3, 1969 E. BARTHOLOMEW 3,447,516

ENG INE IMPROVEMENTS Filed July 21, 1966 Sheet To Tlzrolile INVENTOREarl BaTZ/zolonzew June 3, 1969 E. BARTHOLOMEW 3,

ENGINE IMPROVEMENTS Filed July 21, 1966 7 sheet 2 A 2M k 268 204 '/212 m276 INVENTOR Earl Barllzolomw 282 29 262 270 fl ldw ATTORNEYS June 3,1969 I E. BARTHOLOMEW 3,447,516 I ENGINE IMPROVEMENTS Filed July 21,1966 Sheet 3 of :s I

. o flfo I -.--'i 11 11 11111 11 1 11111111111 111111111111 111 1111 rINVENT OR Earl i Bari/1010116610 Bwonw fi ATTORNEY United States Patent3,447,516 ENGINE IMPROVEMENTS Earl Bartholomew, Birmingham, Mich.,assignor to Ethyl Corporation, New York, N.Y., a corporation of VirginiaContinuation-impart of applications Ser. No. 408,135, Nov. 2, 1964, nowPatent No. 3,282,261, Nov. 1, 1966, and Ser. No. 443,956, Mar. 30, 1965,now Patent No. 3,310,045, Mar. 21, 1967, the first of which is acontinuation-impart of applications Ser. No. 301,249, Aug. 12, 1963, andSer. No. 314,814, Oct. 12, 1963, now Patent No. 3,198,187 Aug. 3, 1965,and the second of which is a continuation-in-part of said applicationSer. No. 314,814, and of application Ser. No. 445,856, Mar. 29, 1965,now Patent No. 3,250,264, May 10, 1966. This application July 21, 1966,Ser. No. 572,635

Int. Cl. F02m 3/04 U.S. Cl. 123-97 7 Claims ABSTRACT OF THE DISCLOSUREGasoline engine induction system for automobile and the like providesless emission of undesirable exhaust products by having fuel cut-0Evalve connected to cut off fuel flow from carburetor when vehicle isdecelerating from speeds of at least about 30 m.p.h. and to restore fuelflow when speed reaches about 22 rn.p.h. Cut-01f can be controlled bycentrifugally operated valve in series with valve responsive toincreases in intake manifold vacuum, or by vacuum-responsive valve alonewhen it has sufiicicnt hysteresis to cause cut-ofi at about 23 inchesand not to restore fuel flow until vacuum drops to about 21.5 inches.Hysteresis can be provided by having cutolf control of snap type or byhaving auxiliary vacuumoperated valve energized by principalvacuum-operated valve and increasing the action of the vacuum. Cut-oftvalve operator can also act as pump to pump a little extra fuel toengine whenever the cut-off is terminated, in which case operator isarranged not to respond to intake manifold pressure changes smaller thanmentioned above. Carburetor can have no idle jet so that engine idles onthe main jet and fuel mixture is then more closely controlled over theentire range of operation. Mixture enrichment is preferably arranged foridle as against off-idle operation, as by having the closing of thethrottle open an external vent in the carburetor bowl or having asupplemental fuel jet opening in throttle barrel alongside idle positionof downstream tip of throttle blade. Better mixture control overoperating range is also obtained by having automatic choke operated bymixture taken downstream from carburetor venturi, heated, and deliveredto thermally responsive choke actuator. Above features can beincorporated in a single small primary carburetor that is combined withone or two large second ary carburetors used for high power operation.Supp1emental heating can be provided for mixture delivered by primarycarburetor.

This application is a continuation-in-part of applications Ser. No.408,135 filed Nov. 2, 1964 (now U.S. Patent 3,282,261 granted Nov. 1,1966) and Ser No. 443,- 956 filed Mar. 30, 1965 (now U.S. Patent3,310,045 granted Mar. 21, 1967), the first of which is in turn aeontinuation-in-part of applications Ser. No. 301,249 filed Aug. 12,1963 (now abandoned), and Ser. No. 3 14,814 filed Oct. 12, 1963 (nowU.S. Patent 3,198,187 granted Aug. 3, 1965), and the second of which isin turn a continuationin-part of said application Ser. No. 314,814 andof application Ser. No. 445,856 filed Mar. 29, 1965 (now U.S. Patent3,250,264, granted May 10, 1966).

The present invention relates to internal combustion engines of the typeused to power vehicles such as autoice mobiles. In operation theexhausts of such engines emit undesirable materials such as unburnt andpartially burnt hydrocarbons and excessive carbon monoxide.

Among the objects of the present invention is the provision of novelinduction systems for such engines, to help reduce their undesirableemissions.

The foregoing as well as other objects of the present invention will bemore fully understood from the following description of several of itsexemplifieations, reference being made to the appended drawings inwhich:

FIG. 1 is a somewhat diagrammatic sectional view of a portion of anengine induction system pursuant to the present invention;

FIG. 2 is a view similar to FIG. 1 but with additional parts brokenaway, showing a modified induction system representative of the presentinventon;

FIG. 3 is a view similar to FIGS. 1 and 2 showing another modifiedinduction system representative of the present invention;

FIG. 4 is also a somewhat diagrammatic sectional view of portions ofanother induction system typical of the present invention;

FIG. 5 is a diagrammatic sectional view of a portion of an inductionsystem representative of the present invention; and

FIG. 6 is also a somewhat diagrammatic sectional view of portions ofanother induction system typical of the present invention.

Acording to the present invention an induction system of an internalcombustion engine propelling a vehicle has a fuel cut-01f control forinterrupting the flow of fuel to the engine when the vehicledecelerates, the control has a first control element shiftable betweenan actuated and a deactuated position in response to vehicle speed, anda second control element connected to respond to a severe drop inpressure in the intake manifold of the engine by causing fuel cut-01f solong as the first control element is then in its actuated position, andthe first control element is connected (a) to be shifted to itsdeactuated position when the vehicle speed is less than about 22 milesper hour, and (b) to be shifted to its actuated position when thevehicle speed is at least about 30 miles per hour.

The fuel cut-oft valves of the induction systems of the presentinvention are also desirably arranged to act as pumps and discharge intothe intake manifold a quantity of fuel when cut-off is terminated so asto provide extra fuel and thus help the engine run smoothly as itresumes operation after the cut-off.

Another feature of the present invention is the provision of a fuelcut-off valve operator arranged to move the valve into cut-off positionin response to a suction at least about 23 inches of mercury belowatmospheric pressure, the operator having suificient hysteresis to keepthe valve in cut-oft position as the suction is diminished in intensityuntil it reaches about 21.5 inches of mercury below atmosphericpressure, and to then open the valve.

To simplify the provision of accurately proportioned fuel-air mixturesfor combustion, the induction systems of the present inventionpreferably have a venturi-containing air supply throat for providingsuction to draw gasoline for operating the engine under part-throttleconditions with a relatively lean fuel mixture such as one having anair-to-fuel ratio at least as high as 15:1, said system having anautomatic choke assembly including a conduit that draws a gaseous streamthrough an engine-heated stove to heat the gas and then deliver the gasto a temperatureresponsive choke valve bias. For accurate maintenance ofthe proportioning the gas conduit is preferably connected to withdrawgas from a point in the throat downstream of the venturi, and toultimately deliver the gas to the intake manifold.

The improvements of the present invention are shown with greater clarityin the drawings. In FIG. 1 a carburetor is illustrated as mounted on anintake manifold 12 and as including a fuel bowl 14, an air horn 16, athroat 18, and a venturi connecting the horn with the throat. Thecarburetor can have a conventional arrangement for supplying a fiow offuel to mix with the air that passes through the venturi, and in FIG. 1only a main fuel jet 22 is illustrated. Jet 22 communicates with thelower portion of fuel bowl 14 by way ofv a cut-off valve 23 having afixed seat 24 and a movable plug 26. The jet may also have specialprovision indicated at for receiving a variable quantity of air,depending upon the ambient temperature, as more fully explained inparent application Ser. No. 445,856.

In the throat of the carburetor there is a throttle valve 32 shown asoperated by means of a linkage 34 extending to a throttle pedal or thelike. The throttle valve can also be provided with a delaying orchecking mechanism to keep the throttle from closing rapidly through itslast few degrees of closing movement, and such checking mechanism caninclude a checking arm 36 that cooperates with a pneumatic, hydraulic orother type of delay structure as shown for example in the various parentapplications.

The cut-off valve plug 26 has a shank 38 by which it is connected to thediaphragm 40 of an operating head 50. The head includes a suctionchamber 42 connected to a suction line 44 and arranged so that theapplication of sufficient suction through that line will cause thediaphragm 40 to be pulled to the right as shown in FIG. 1, against theresistance of a return spring 46. Relieving of the suction permits thespring to return the diaghragm to the left-hand position.

Head is also arranged to operate as a pump. To this end a space 52 onthe side of the diaphragm opposite suction chamber 42 is sealed andprovided with fuel inlet and outlet tubes 54 and 56 which containappropriate check or one-way valves 58 and 60. Inlet tube 54communicates with fuel bowl 14 to receive fuel from that bowl, whileoutlet tube 56 leads to a discharge opening 62 in carburetor throat 18,downstream of throttle valve 32. A complete cycle of fuel cut-oft valveoperation will accordingly first draw fuel into pump space 52 as thediaphragm moves to the right, and when the diaphragm returns to theleft-hand position will cause that fuel to be discharged into thecarburetor throat.

The application of suction to suction line 44 is effected by cut-offcontrol which includes a control valve 72 and a suction line 74. Valve72 is of the sliding spool type, having a spool 76 shiftable in ahousing 78, a recess 80 in the spool providing communication betweensuction lines 74 and 44 when the spool is appropriately positioned, asillustrated. This is the right-hand position of the spool which can alsobe moved towards the left, thereby breaking the connection between thetwo suction lines. A vent 82 can also be provided to rapidly ventsuction line 44 when the spool is in its left-hand position.

The spool is secured to a rod 84 which has a reduced extension 85 thatpivotally receives a centrifugal operator 86 rotatably fitted over therod and held by a fixed support mount 95. The centrifugal operator isrotated by the vehicle or engine, as by means of belt 88 and pulley 89formed on the operator, and has a rotatable collar 90 slidable along thereduced portion 85 of spool rod 84 between two collars 91, 92 fixed onthat rod. Springs 93 may be provided to urge the rotatable collar 90toward collar 91.

The cut-ofi control 70 further includes a vacuum cylinder having apiston 102 and a suction chamber 104 connected to the intake manifold bya suction supply line 106 arranged so that the application of sufiicientsuction through that line will cause the piston 102 to move to the rightagainst the influence of a coil spring 108, as shown in FIG. 1. Thepiston 102 has a piston rod 110 connected to a slide valve 66 so thatmovement of the piston to the right also causes the recessed portion 114of that valve to connect the suction line 74 to the supply line 106. Avent such as 116 can be provided to rapidly vent the supply line 74 whenthe recessed slide valve 112 is in its left-hand position.

In use, the induction system of FIG. 1 operates to supply fuel to thecarburetor throat when the engine in which is is incorporated is runningat any speed, and is not abruptly decelerating. When the vehicle drivenby such engine begins rapid deceleration, the intake manifold suctionwill be sufficiently intense to cause the piston 102 to move to theright compressing coil spring 108. The coil spring may be preloaded sothat the piston moves to the right at a manifold vacuum slightly abovethe highest vacuum developed when there is no deceleration. When thepiston 102 shifts to the right, the recessed portion 114 of the slidevalve 66 connects the vacuum supply line 106 with the line 74. At speedsof 30 miles per hour or over the governor control 86 moves the spool 76to its right-hand position so that manifold suction is supplied to thecut-off valve operating head and fuel flow is cut 01f.

As deceleration proceeds, the intensity of the manifold suction willdiminish and the centrifugal operator will gradually move its collar 90toward fixed collar 91. When deceleration proceeds to about 22 to 25miles per hour, the centrifugal operator moves the valve spool 76 to theleft, breaking the suction connection to the cut-off valve andpermitting spring 46 to open the cut-off valve and restore the fuelflow.

The centrifugal action of the control 86 is much more accurate anddependable than intake suction variations in determining when the fuelflow is to be cut oif and restored. It is accordingly preferred to havethe centrifugal action govern the cut-off valve operation in accordancewith engine or automobile speed, as by arranging for the suction head 50of that valve to close the cut-off valve in response to a degree ofsuction not quite as intense as will be developed during the desireddeceleration. In this way whenever the spool valves 76 and 66 are bothmoved to their right-hand positions the manifold suction will always besuflicientl-y intense to effect shut-off. Correspondingly, some droppingoff of suction intensity during deceleration will not open the cut-offvalve until the spool valve 72 moves to its left-hand position. Asindicated above, the apparatus can accordingly be adjusted to preventfuel cut-off unless the deceleration starts from at least 30 miles anhour, and restoration of fuel flow can be adjusted at 22 to 25 miles perhour. At any time during the deceleration, opening of the throttle, asby depressing the throttle pedal, will cause the manifold vacuum todecrease which then causes the spring 108 to move its piston 102 to itsleft-hand position, terminating the fuel cut-off so that the engine isimmediately available for doing whatever work is called for. Preferably,the centrifugal operator is responsive to automobile speed rather thanengine speed to minimize the possibility of fuel cut-ofi? dur ing gearshifting.

Along with the foregoing, every fuel cut-01f termination will beaccompanied by the pumping of additional fuel into the induction systemfrom pump space 52 through outlet tube 56 and discharge opening 62 sothat engine firing commences immediately and does so smoothly whetherthe resumption of firing is merely for idling the engine or for thebeginning of a violent acceleration.

It has been discovered that best operation with exceedingly low levelsof undesired exhaust emission is obtained when the fuel flow resumptionis at a vehicle speed only slightly below the 30 miles per hour minimumspeed at which cut-off is effected. The difference in the two speeds isso small that manifold suction cannot be depended upon to accuratelyprovide the sole control.

The construction of FIG. 1 involves a very small number of componentsand can be further simplified by having its centrifugal operator 86combined with the conventional type of centrifugal ignition advancingmechanism operated by the distributor shaft. An extra set of fiy-weightson such shaft can be provided for this purpose although it is alsopossible to use for the cut-off mechanism the same weights that arerelied on to advance the timing.

The construction of FIG. 2 is a still further simplified embodiment offuel cut-off arrangement in accordance with the present invention. Inthis construction no centrifugal or speed-responsive control is used,and the intake manifold suction directly effects the cut-off andrestoration of fuel flow by means of a snap action valve operator 150.Operator 150 is similar to operator 50 of the construction of FIG. 1,but has a snap disc 140 made of spring sheet metal that has been given apermanent deformation to form abulge with a perforated center. The metalof the disc is thin enough so that some force applied to the outsidebulge will cause it to snap into inside-out position forming a reversebulge. Because of the springiness of the metal the removal of theforegoing force will permit the disc to snap back into its originalposition. Both snaps take place abruptly and the snapped disc does notshow any tendency to remain in any position intermediate between theextremes to which it snaps.

In many respects the fuel cut-off arrangement illustrated in FIG. 2operates in a manner similar to the arrangement shown in FIG. 1 tosupply fuel to carburetor throat 118 when the engine in which thisarrangement is utilized is running at any speed and is not abruptlydecelerated. Compression spring 146 then functions to keep the cutoffvalve plug 126 away from its seat 124 because there is insufiicientsuction in the manifold 112 to draw the snap disc 140 to its right-handposition where it would cause the cut-off valve to close. When thevehicle driven by the engine in which this arrangement is incorporatedbegins rapid deceleration, the intake manifold suction will besufiiciently intense to snap the disc 140 to the right and therebyterminate the supply of fuel.

The cut-off valve plug 126 remains in the closed position until themanifold suction diminishes to a predetermined intensity at which thedisc 140 snaps back to its original position which in turn unseats thevalve plug. Since the force required to hold the snap disc inside out isless than that needed to initially move the disc to that position, itaccordingly follows that the cut-0E valve plug 126 will remain seatedover a range of manifold suctions in a manner similar to the way thespeed-responsive device of FIG. 1 keeps the cut-off valve closed over arange of engine speeds. Thus, for example, the snap disc can be so madethat it moves the valve to fuel cut-off position when subjected to asuction of at least 23 inches of mercury below atmospheric pressure, andto have sufficient hysteresis to keep the valve closed as the suction isdiminished in intensity until it reaches about 21.5 inches of mercurybelow atmospheric pressure, at which point the disc will Snap back andopen the valve to thereby terminate fuel cut-off.

Along with every cut-off termination additional fuel is pumped into theinduction system from pump space 152 on the side of snap disc 140opposite the suction chamber through outlet tube 156 in the same manneras described above in conjunction with the cut-off arrangementillustrated in FIG. 1.

Another simplified embodiment of a fuel cut-off arrangement inaccordance with the present invention is shown in FIG. 3. As in theconstruction of FIG. 2, no centrifugal or speed-responsive device isused to control the operation of the valve, and the intake manifoldvacuum effects the cut-off and restoration of fuel flow by means of acontrol assembly 262 having a pair of vacuum cylinders 264, 266 withpistons 270, 280 linked together through a slide valve 268.

The first vacuum cylinder 264 includes a suction chamber 272 connectedto intake manifold 212 by a suction line 274 arranged so that theapplication of sufficient suction through that line will cause thepiston to be pulled to the right as shown in FIG. 3, against theresistance of compression spring 276 in the same manner as explained inconjunction with FIG. 1. Movement of the piston 270 to its right-handposition also causes the recessed portion 278 of the slide valve 268 toconnect tube 244 to suction line 274. Manifold suction is then appliedto the flexible diaphragm 240 of the operating head 250 by way of line244 to thereby cause the valve plug 226 to cut off the fuel fiow asexplained above in conjunction with FIG. 1.

Vacuum cylinder 266 also includes a suction chamber 284 whichcommunicates with tube 244. Accordingly when the suction in line 274 isabove a predetermined intensity, piston 270 is drawn to the right, slidevalve 268 and piston 280 moving along with it so that intake manifoldsuction is also applied to chamber 284.

In operation, the second vacuum cylinder 266 serves as a holding orhysteresis device to prevent the piston 270 from shifting back to itsleft-hand position until the manifold suction diminishes to apredetermined lower intensity corresponding to that at which the fuelflow is to be restored.

By way of example, vacuum chamber 272 may be so dimensioned that amanifold suction of at least 23 inches of mercury below atmosphericpressure is required to create a force on the piston great enough tocause it to compress spring 276. This suction would then be applied tothe diaphragm 240 by Way of the slide valve 268 and the line 244 toclose the cut-off valve, and it will also bring vacuum cylinder 266 intoaction. The combination of cylinders 264 and 266 then requires lessintense suction to hold valve 268 in its right-hand position. Fuelcut-off termination would not occur until the manifold suction reached,for example, 21 /2 inches of mercury below atmospheric pressure at whichtime the spring 276 would urge the piston 270 to the left, therebycausing the slide valve 268 to break the suction connection to thecut-off valve and permitting the spring 246 to open the valve andrestore the fuel flow.

As in the construction of FIGS. 1 and 2, along with every fuel cut-offtermination additional fuel is pumped into the induction system frompump space 252. Moreover, as in the construction of FIG. 1, the suctionchamber 242 is only exposed to manifold vacuum when fuel cut-off isdesired. This is particularly important with the fuel cut-off valve ofthe continuous travel type which can move back and forth with smallpressure fluctuations in the manifold, thus causing small amount ofunwanted fuel to be pumped into the induction system through line 256.

The induction systems illustrated in FIGS. 1-3 may include an automaticchoke assembly of the type illustrated at 300 in FIG. 4 which operatesto bias a choke valve 302 toward a closed position during cold enginestarting and warm-up. The choke valve 302 is connected through linkage304 to an arm 305 fixed to one end of a rotatable shaft 303. The end ofshaft 303 opposite the one connected to linkage 304 carries an arm 311connected to a piston 312 loosely fitted in a pneumatic cylinder 313,and arm 311 has an extension 307 connected to a free end of bimetallicor similarly thermally-responsive coil spring 306, the other end ofwhich is fixed and which is calibrated to resiliently urge the chokevalve closed when the engine is cold. The coil is enclosed by a suitablehousing 308 that defines a compartment 309 having an inlet port 310connected to the outlet of a choke stove (not shown). The compartment309 communicates with the cylinder 313 by way of the clearance aroundits loosely fitted piston 312, and the cylinder in turn has alongitudinally extending discharge port 315 leading to an intakemanifold conduit 317.

. The choke stove, which is conveniently mounted on the exhaust system,has an inlet running to a conduit 318 that opens at 320 inside thecarburetor throat in a direction that points upstream. Aside from thislocation of the choke stove inlet, the entire choke system can be ofconventional construction, with the tension of the thermostatic coil306, when cold, urging choke valve 302 closed until the engine isstarted and the air then entering the air horn 316 causes the valvewhich is unbalanced to open somewhat against the bias of thetemperature-responsive thermostatic coil. At the same time intakemanifold suction is applied by means of conduit 317 to the choke piston312 and also tends to pull the choke valve 302 open.

The manifold suction also sucks gas from the compartment 309, causingsome of the fuel-air mixture to be drawn from the carburetor throatthrough stove inlet 318. Heating of this mixture as it passes throughthe choke stove warms up the spring coil 306 so that it relaxes itstension.

As the engine warms up, the choke piston moves farther and farther tothe right, as seen in FIG. 4, reducing but not completely cutting offthe -flow through the choke stove. This assures the maintenance of thespring coil 306 in fully warmed-up condition during further operation ofthe engine.

By drawing the warm-up medium from the carburetor throat downstream ofthe venturi, the variations in warmup flow of this medium with engineoperating changes will not change the fuel-to-air proportion in themixture delivered to the cylinders. All the air in such mixture mustnecessarily pass through the venturi (except for very slight leakagethrough throttle valve shaft journals or the like) so that the mixturecan be more accurately metered. No excessive richening of the mixture istherefore needed to make up for the variable air leakage through thechoke system ordinarily experienced where the choke stove inlet isupstream of the venturi.

The foregoing choke improvement is particularly effective where thecarburetor venturi is used to provide idle combustion mixture as well asthe combustion mixture for operating the engine at higher speeds andpowers. It will be noted in this connection that the construction ofFIG. 4 has no idle fuel jet such as is conventionally used in engines.As explained in parent application Ser. No. 443,956, the idle fuel jetcan be omitted where the venturi is made small enough to operateeffectively with the low air flow rate developed at idle, and this isconveniently accomplished by having the throttle arranged to providewhen closed a minimum mixture flow passageway with a cross-sectionalarea at least about 6 to 10% that of its maximum passageway when wideopen. As in that application the throttle plate in the construction ofFIG. 4 can be perforated.

Inasmuch as the carburetor of FIG. 4 is, by reason of the absence of theusual idle mixture, readily adjusted to provide accurately proportionedfuel-air mixtures over the entire range of its operation, suchadjustment can be made to give stoichiometric mixtures which results inextremely low exhaust emission. Leaner mixtures such as a 17:1 air fuelratio will produce further reductions in exhaust emission and theseleaner mixtures can be used in dual intake manifold systems such asdescribed in application Ser. No. 408,135. Combining the carburetorstructure of FIG. 4 with the fuel cut-E features of FIGS. 1-3, and ifdesired also adding a throttle-closing delay as described in the parentapplications, gives an extremely efiicient induction system and one thathas a strikingly low emission of carbon monoxide as well as of unburntand partially burnt hydrocarbons.

For best operation the fuel-air mixture metered by the carburetor ispreferably slightly richer at idle than under load. Such an arrangementenables smoother and more stable idling as compared to having the samemixture ratio for both types of operation.

In the construction of FIG. 4 a very small idle enrichment is providedby a vent 327 that opens to the atmosphere directly from the fuel bowl314, when the throttle is in idle position, but is closed by flap 329under all other throttle positions. When closed the fuel bowl is ventedthrough vent tube 331 to the carburetor air horn 316 where the pressureis slightly below atmospheric during engine operation.

Flap 329 is shown as pivoted at 333 and as having a lever arm 335 biasedupwardly by spring 337 to urge the flap toward vent-closing position. Asoft gasket 339 below the flap helps assure effective vent closing. Alink 341 connected between flap lever 335 and the throttle control isvertically reciprocable and is moved downwardly by a crank arm 343mounted on the throttle shaft when the throttle moves into idleposition, thus causing vent 327 to open. Opening of the throttlereleases the link 341 and permits spring 337 to close the flap over thevent.

The extra idle enrichment of the present invention can be provided byother arrangements such as a very small idle port, and can amount toonly a small fraction of an air-to-fuel ratio. The idle ratio canaccordingly be 14:1 with the operation ratio 15: 1. In very warmclimates, however, the idle mixture can be leaned down to 14.5: 1.

FIG. 5 shows a particularly desirable idle enrichment technique. In thisfigure a relatively small fuel port 382 is positioned within the throat384 of a carburetor such as that of FIG. 4. The port opens into thethroat alongside the downstream tip 388 of a throttle plate 390 suitablyjournaled in the induction passage. The plate is perforated as indicatedat 386 to permit the passage of idle fuel mixture even though the plateis in fully closed position. During such idle operation a small amountof fuel is sucked into the throat from the fuel bowl 392 throug the line394 and the port 382. By locating the port opening alongside thedownstream tip of the throttle plate below the upper edge of the tip andpreferably as illustrated between the upper and lower edges of the tip,fuel flow through the port is cut off quickly whenever the throttle isopened even a small amount. As little as 5 of opening will leave theport etfectively exposed to the ambient pressure above the throttle,which is not low enough to suck the fuel up from the fuel bowl.

Such at 5 limit on the enrichment operation is particularly desirablewhen operating with lean mixtures, that is mixtures having air-to-fuelratios at least :as high as 15:1. The idle enrichment is then essentialto smooth idling so that the idling speed can be set to a relatively lowvalue, generally not over 600 r.p.m., and the engine can then make fulluse of the fuel economy and low exhaust undesirables of the leanmixtures.

Permitting the enrichment to continue to 10 throttle opening (aboveidle) would carry the enrichment into a large portion of the engines lowspeed operations when used to power an automobile. Most presen-dayautomobile engines are so powerful that in city traflic they need neverhave their throttle opened more than about 10.

The need for idle enrichment diminishes as the idle engine speedincreases. At 700 r.p.m. idle enrichment is still desirable, but at 800r.p.m. it can be completely dispensed with.

As pointed out in the parent applications, the use of lean mixturescalls for a carburetor venturi of relatively small cross-sectional area.Thus for 16.5 :1 mixtures (before idle enrichment) the venturi (orventuris where more than one is used) should have a combinedcross-sectional area at their minimum point of about 0.1 to 0.2 squareinch per hundred total cubic inches displacement.

Although the port 382 of FIG. 5 may simply be a non- =adjustable meteredorifice in view of the very small amount of fuel it passes, it can bemade adjustable by providing for, for example, a threaded screw 396having a tapered end portion 398 that coacts with the port passageway toadjust its effective size. Additionally, the undesirable of the throttleplate may be recessed as at 399 to enable the port to be as high aspossible and not have it obstructed too much by the throttle plate. Arecess of this type is essential where the plate tip, instead of beingrectangular, has its edge face tapered so that essentially the entireedge face engages the throat wall.

Vent 327 of the construction of FIG. 4 may also be made adjustable as byhaving flap 329 bendable to positions in which it partially blocks thevent even when the flap is lifted as far as it will go.

The line 394 is preferably provided with an air bleed so that the fuelsupplied through the port 382 is in the form of an emulsion.Alternatively the bleed can be omitted and the port made somewhatsmaller in crosssectional area.

Where the throttle plate is held open during idle, as for instance whenthe perforations 386 are not present, the enrichment port stillpreferably opens at a level between the upper and lower edges of theplate tip when the plate is in idle position. However the recessing ofthe lower face of the plate is then not needed.

In conventional carburetor systems where idle fuel is normally suppliedby one or more fuel ports located under the upstream tip of the throttlevalve, a small fuel port positioned under the downstream tip of thevalve can be provided to improve the operation of the carburetor. Thefuel port positioned alongside the downstream tip of the valve providesa portion of the idling fuel which can be cut off abruptly and much morequickly than the fuel from the conventional ports when the throttlevalve moves away from idling position. Such an arrangement reducesover-rich conditions at slightly off-idle positions which in turnreduces undesirable exhaust emissions.

The choke and enrichment features of the construction of FIGS, 4 and 5are particularly valuable when used together and also when used withprimary carburetion barrels in a multiple carburetion system. Such anarrangement is shown in FIG. 6 which illustrates an intake manifold 400for a V-8 engine, the manifold being equipped with a unitarythree-barrel carburetor 410 having barrels 411, 412, 413. Thecombination is shown in sectional view, the section taken transverselyof the engine crank shaft direction. The manifold has an upper wall 404with three openings 401, 402, 403 very close together and they are shownas only separated by a sufficient amount to allow for locating securingbolts between them. They can be spaced even closer together by shiftingthe mounting bolts to other locations and can in fact be spaced apart aslittle as a half inch if desired, or even less. The space between thebarrels is conveniently used to provide room for a common float chamber420 so that this chamber can be essentially confined within the outerlimits of the three barrels themselves. This greatly reduces the spaceoccupied by the carburetor.

Mixture-receiving openings 401, 402, 403 are shown as opening downwardlyinto a transverse distributor section 405. Each transverse end may bebranched to provide four outlets for the respective four cylinder intakeports at each bank of the V8 engine. The usual heating duct cross-overbetween opposing exhaust ports in the two banks is shown as havingbranches 406, 407, branch 406 penetrating through distributor section405 to provide more direct heating for the intake mixture passingthrough the section particularly from barrel 411. Branch 407 runsbeneath the floor for distributor section 405 to provide further heatingof the intake mixture. Heating the fuel mixture in such a mannerprovides better distribution of the fuel to the engine. Heat-transferribs 408 can also be provided on the floor to further improve heattransfer.

Carburetor barrel 411 is the primary barrel on which the engine isoperated under low power and cruising conditions, and it is relativelysmall as compared to the crosssectional area made available by theintake manifold for carrying the mixture to all cylinders. As pointedout in application Ser. No. 408,135, a primary barrel with a venturiarea only about that of the total venturi area when all carburetorbarrels are in use, operates surprisingly well under part-throttleconditions with a mixture ratio of 16:1, which is leaner than heretoforeconsidered practical, Such operation produced a hydrocarbon emission ofonly 112 parts per million in a standard V-8 engine that had its intakemanifold modified to permit running on a small primary carburetor barrelwith a venturi-throat-cross-sectional area of 0.16 square inch per cubicinches of total piston displacement. The manifold was originally of thestandard two-barrel carburetor type and was modified by removing itscommon wall, a partition 1 A inch deep by 1% inch long known as theriser partition. Thus, the manifold was converted to one in which acommon passageway branched to all cylinders. By contrast a standardfour-barrel induction system on this engine produced hydrocarbonemission of 240 parts per million when operated with a 16:1 fuel ratio.

Similar results have been obtained on a large V8 engine that had itsintake manifold modified to take three carburetor barrels. The manifoldwas originally of the standard four-barrel type with four intakeopenings, two for primary barrels and two for secondary barrels. Each ofthe primaries was paired with a different secondary, and each pair ledthrough a longitudinal runner and then through lateral branches to halfthe cylinders of the engine, two in each bank. The half not supplied byone runner was supplied by the other. The modification consisted ofmilling out a section 1% inches deep by 1%, inches long in the webbetween the manifold halves at the primary intake openings. A primarycarburetor barrel was mounted over the center of the common chamberformed by this operation and the two secondary carburetor barrels wereattached concentrically with the two secondary openings in the manifold.The primary carburetor had a venturi throat which was 15% of thecombined cross-sectional area of the three venturi throats and 0.15square inch per 100 cubic inches of total piston displacement. A vehiclehaving an engine with this type of induction system has emitted onlyparts per million hydrocarbons and 0.4% carbon monoxide during a testcommonly used to evaluate automobile exhaust emissions, as opposed to476 parts per million hydrocarbons and 2.7% carbon monoxide emitted bythe same car with a standard induction system. The car with the modifiedinduction system has proved to be driveable with mixture ratios of 17pounds air per pound fuel.

In another embodiment a standard four-barrel manifold with two separatelongitudinal runners was modified to take three carburetors in atransverse arrangement, The partition between'the two runners at theprimary openings was milled away to a depth of one inch and separateoutwardly directed lateral passageways were added to each longitudinalrunner adjacent the intake openings, with a large secondary carburetorfitted on each lateral. The original secondary intake openings werecovered and a primary carburetor fitted over the four intake openings.The roof of the heat cross-over for the standard manifold was used as afloor for the lateral passageways to provide a heated surface under eachsecondary carburetor.

The primary carburetor had a bore 1.1 inches in diameter and a venturi0.88 inch in diameter, while the two secondary carburetors each had abore 1% inches in diameter and a venturi 1% inches in diameter. Theprimary venturi area was 0.12 of the combined cross-sectional areas ofthe two longitudinal runners, and 0.16 square inch per 100 cubic inchesof total piston displacement, which piston displacement corresponds toabout 70 horsepower of maximum power output. The net venturi area of theprimary carburetor was about 11% of the total net venturi area of thethree carburetors.

The modified assembly operated very well with primary barrel mixtureratios as rich as 15: 1, only began to misfire when the ratio reachedabout 20:1 or leaner and over this entire range showed very littlehydrocarbon emission.

Similar results are obtained when only one secondary 1 1 barrel havingtwice the throat and venturi areas of one of the foregoing secondarybarrels, is substituted for both of the secondary barrels in thatcombination. Such substitution is preferred for use with in-line enginessuch as the more conventional six-cylinder automobile engines inasmuchas it materially simplifies the induction systern without detracting fromits efliciency. On the other hand forV-type engines and particularlyV-8s, it is preferred to have a pair of secondary barrels because theyprovide better induction and take up less space than a single largersecondary barrel.

The ratio of primary venturi area to total venturi area or to totalcross-sectional area of manifold passageway can be as low as 5%, and theprimary venturi area can be as low as about 0.1 square inch for every100 cubic inches of total piston displacement or for every 70 horsepowerof maximum engine output, and still give very good opera tion,particularly with large engines such as used in large trucks and buses.

Increasing the relative size of the primary venturi beyond about 0.2square inch for every 100 cubic inches of total piston displacementreduces the effectiveness of the operation with lean mixtures. At thisproportion the primary venturi area is about /a the combined area of allventuris.

It is preferred that the primary barrel be so small that the airvelocity through the most restricted portion of its venturi be about 200to 300 feet per second when the engine is operating under road loadcruise at 1100 r.p.m. Conventional 4-barrel carburetors generallyprovide an air velocity of only about 60 feet per second in suchoperation.

Because of the relatively small size of the primary barrel as comparedto the intake manifold dimensions, it is helpful to provide additionalheating for the mixture supplied by that barrel. In FIG. 6 an extrashelf 406 is provided directly under opening 401, which shelf is theupper surface of the exhaust crossover 406. By having this shelf onlyabout to 1 inch below opening 401, fuel droplets delivered by barrel 411will impinge directly on the shelf and volatilize as well as break up,to be carried away by the mixture movement with very little tendency toaccumulate as a liquid pool on the floor of the manifold.

Instead of having the intake manifold arranged with its trunk passage ordistributor section 405 running transversely of the engine, it couldalso run longitudinal of the l e 1 I" engine as 111 conventlonal V-8manifolds, with branches running to the individual cylinders from thelongitudinal ends. With either arrangement it is preferred to have thethrottle plates pivot about axes that are longitudinally directed, thatis parallel to the crank shaft. Such an orientation gives betterdistribution of mixtures to the cylinders in both banks of the engine.

The fuel-metering arrangements of primary barrel 411 are essentiallylike those shown in applications Ser. No. 408,135 and Ser. No. 443,956,but the secondary barrels have auxiliary ports 472 that supply fuel whenthe secondary throttles are only slightly opened and not enough air ispassed to operate their venturis.

The throttle of the primary carburetor barrel is also provided with athrottle-closing delay shown in FIG. 6 in the form of a dash-pot 470that causes the throttle to close slowly in the event the throttlecontrol is abruptly closed after the throttle-closing movement gets tothe point that the air or mixture flow in the barrel reaches about poundper hour per cubic inch displacement. The delayed rate of closure thencan be about 5 to 10% per second, as described in Ser. No. 408,135, andthe dash pot construction can be the same as there described.

In addition, the throttle check is arranged to hold the minimum air flowrate somewhat above the idle limit for as long as possible, generally upto about 25 seconds after the beginning of a deceleration from aboutmiles per hour for an automobile driven by the engine of FIG. 6. Theextra air of the mixture flow provided by the last few seconds ofchecking can be such that about 20 to more flows through the barrel thanthe minimum for idling at no road load with 6 ignition advance beforetop center. After the throttle checking is completely terminated thethrottle returns to the usual idle setting with the engine running atabout 600 r.p.m. or somewhat less, and the ignition timing about 6before top center.

The constructions of FIGS. 1, 2, 3 and 6 are particularly effective whenused with automobiles having all mechanical transmissions, that is thetype called manna Such all-mechanical transmissions rigidly connect theengine to the automobiles wheels and such connections give the greatestconcentration of undesired exhaust emissions during deceleration of theautomobile. Automobiles that have fluid-coupled transmissions such asthose called automatic, permit the engine to slow down much moreabruptly than the vehicle does during deceleration and for this reasongive much lower concentrations of undesirable exhaust emission duringdeceleration.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

1. An automatic fuel cut-off valve for an internal combustion engine,said valve including a suction-head operator having a diaphragmconnected to move the valve to fuel cut-01f position when subjected to asuction at least about 23 inches of mercury below atmospheric pressure,said diaphragm having suflicient hysteresis to keep the valve closed asthe suction is diminished in intensity until it reaches about 21.5inches to mercury below atmospheric pressure, and to then move the valveto fuel flow position.

2. An induction system for an internal combustion engine, said systemhaving fuel supply elements, a fuel cut-off valve and an on-oif suctioncontrol that responds to the pressure in the intake manifold of theinduction system by moving to on position at one pressure and to ofifposition at a substantially diiferent pressure, said control beingconnected to cause the valve to move to off position when the manifoldvacuum drops to 23 inches of mercury below atmospheric pressure and tothen keep the valve in off position until the manifold vacuum reachesabout 21.5 inches of mercury below atmospheric pressure.

3. The combination of claim 2 in which the suction control includes aprimary vacuum cylinder connected to cause the valve to move to fuelcut-off position when the manifold vacuum drops to 23 inches of mercurybelow atmospheric pressure and a secondary vacuum cylinder that thencooperates with the primary cylinder to keep the valve closed until themanifold vacuum reaches about 21.5 inches of mercury below atmosphericpressure.

4. In a gasoline engine induction system having an automatic fuelcut-off valve assembly connected to automatically cut off the flow offuel to the engine when the suction in its intake manifold reaches :apredetermined high intensity, to automatically reestablish the flow offuel when the suction diminishes to a predetermined lower intensity, andto automatically pump extra fuel for the engine when the flow isre-established, the improvement according to which the predeterminedhigh intensity is substantially higher than said predetermined lowerintensity and the cut-off valve assembly is connected for 13 actuationin the cut-off direction only when the manifold suction reaches saidpredetermined cut-off intensity.

5. The combination of claim 4 in which the fuel cutoif valve assembly isconnected for actuation by suction delivered from a suction-operatedvalve.

6. The combination of claim 4 in which the fuel cutoff valve assemblyhas a snap-type cut-off valve.

7. The combination of claim 1 in which the diaphragm is a snap-typediaphragm.

l 4 References Cited UNITED STATES PATENTS 10/1959 Dietrich.

6/1966 Walker.

WENDELL E. BURNS, Primary Examiner.

US. Cl. X.R.

